Quantitative hydrogeology of volcanic lakes: Examples from the central Italy volcanic lake district

Volcanic lakes are surface expressions of the hydrogeology of volcanic complexes. Hydrogeological analysis of volcanic complexes is important both in terms of management of the water resource and from the point of view of associated geothermal and volcanic processes. In particular volcanic lakes are the site of possible mixing between superficial fluids (water) and endogenous fluids (gas and/or magma). The Tyrrhenian volcanic domain hosts several volcanic lakes, which, depending on their origin, can be classed as crater lakes or caldera lakes. The presence of large cities (like Rome), and intense industrial and agricultural activities have significantly modified the “natural” equilibrium and groundwater resources have been significantly depleted during the last 20-30 years. In many areas the situation has turned “critical”, involving both the lowering of groundwater and lake levels. In this chapter, we present the results of quantitative hydrogeological analysis of two volcanic lakes in the surroundings of the densely urbanized hinterland of Roma capital city (Italy): the Bracciano caldera lake basin (Sabatini volcanic complex) and the Albano crater lake basin (Colli Albani volcano). The groundwater flow systems have been analyzed and the hydrogeological water balances defined. A focus has been put on the areas with larger aquifer depletion. The methodologies applied to the lake water balances include GIS analyses supported by geostatistics.